In some versions of Little Musgrave recorded in North Carolina, instead of "the little foot page," the snitch who turns Musgrave in is "little Robert Ford." Cas Wallin sang it this way, as did his nephew Dillard Chandler. Cas paused after singing "Little Robert Ford" and chuckled, saying "he got around, didn't he?" showing that he was perfectly aware that Ford had simply become a shorthand for "villain," the Judas of American folksong.

One thing to remember, by the way, is that the US as it exists today is an almalgamation of the old Union and Confederacy. Jesse may have been a villain to the Union but he was a hero to the Confederacy. During the aftermath of the war, that was bound to make him a "folk hero" to many of the downtrodden former rebels. This is one reason why he comes down to us as a folk hero; it was one of the widespread perspectives that existed close to his lifetime.

Meanwhile, no one likes a traitor, so Robert Ford may have done the world a favor, but he did it in a way that was bound to make him a "folk villain." When singers needed a name for the snitch in Musgrave, Robert Ford seemed a natural choice.

BTW, Cas's version of Musgrave is available on a great set of field recordings by Mike Yates, called Far in the Mountains. It's available from Musical Traditions, http://www.mustrad.org.uk
Dillard Chandler's is on an old Folkways LP, available as a custom CD from Smithsonian Folkways.